Swelling raisins and shrinking grapes....osmosis

[ash_wolf]

hi...there was this experiment in my bio text on osmosis about how when you leave raisins in water for some time they swell up and even burst, adn when you place grapes in a strong sugar solution, they shrink....well, i tried these out at home: the raisins surely blew up...but the grapes did not change at all even after a week in sugar solution!!

any possible explanations about this happening? or are my chosen grapes just plain stupid...?

[foodchain]

hi...there was this experiment in my bio text on osmosis about how when you leave raisins in water for some time they swell up and even burst, adn when you place grapes in a strong sugar solution, they shrink....well, i tried these out at home: the raisins surely blew up...but the grapes did not change at all even after a week in sugar solution!!

any possible explanations about this happening? or are my chosen grapes just plain stupid...?

 

You can study such in the difference between vascular and non vascular plants also, water is polar, which has an impact on its interactions with the cell wall if memory serves, or water is polar in regards to the cell walls, which might be somewhat a link to your experiments.

[ash_wolf]

hmm....ok....i'll try them out...but why didn't my experiment with the grapes work out?

[SkepticLance]

For your grape experiment, try a saturated sugar solution, and try scoring the grapes to provide a gap in the grape skin.

 

To make a saturated solution, boil the water, stir in as much sugar as it will dissolve, and let cool. A lot of sugar will fall out of solution, and what remains is saturated.

[dttom]

so to perform your osmosis experiment, what you need is just a selectively permeable member, so if the grape skin is scretched, I think it would not matter. on the other hand, I doubt if the grape skin is not permeable to water, if it is not, so certainly water could not get across the grape skin and your experiment failed, as I am not sure whether it is permeable to water, I can't decide it now.

[SkepticLance]

Hi dttom

 

If the grape skin is not permeable to water, obviously it won't work. However, the inside of the grape is full of cells, each with a semipermeable membrane. So if the skin is broken, osmosis should work.